Add some stuff to NanoImage to make it usable

dgl/NanoVG.hpp

@@ -37,11 +37,21 @@ START_NAMESPACE_DGL
 class NanoImage
 {
 public:
+   /**
+      Constructor for null image.
+    */
+    NanoImage() noexcept;
+
    /**
       Destructor.
     */
     ~NanoImage();
 
+   /**
+      Check if this is a valid image.
+    */
+    bool isValid() const noexcept;
+
    /**
       Get size.
     */
@@ -52,6 +62,12 @@ public:
     */
     void updateImage(const uchar* data);
 
+   /**
+      Operator =.
+      Takes the image data from @a img, invalidating it.
+    */
+    NanoImage operator=(NanoImage img) noexcept;
+
 protected:
    /**
       Constructors are protected.
@@ -62,12 +78,9 @@ protected:
     NanoImage(int w, int h, const uchar* data);
 
 private:
-    NVGcontext* const fContext;
-    const int fImageId;
+    NVGcontext* fContext;
+    int fImageId;
     friend class NanoVG;
-
-    DISTRHO_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR(NanoImage)
-    DISTRHO_PREVENT_HEAP_ALLOCATION
 };
 
 // -----------------------------------------------------------------------

dgl/src/NanoVG.cpp

@@ -85,6 +85,20 @@ NanoVG::Paint::operator NVGpaint() const noexcept
 
 static NVGcontext* sLastContext = nullptr;
 
+NanoImage::NanoImage() noexcept
+    : fContext(nullptr),
+      fImageId(0) {}
+
+#if 0
+NanoImage::NanoImage(NanoImage& img) noexcept
+    : fContext(img.fContext),
+      fImageId(img.fImageId)
+{
+    img.fContext = nullptr;
+    img.fImageId = 0;
+}
+#endif
+
 NanoImage::NanoImage(const char* filename)
     : fContext(sLastContext),
       fImageId((fContext != nullptr) ? nvgCreateImage(fContext, filename) : 0) {}
@@ -103,6 +117,11 @@ NanoImage::~NanoImage()
         nvgDeleteImage(fContext, fImageId);
 }
 
+bool NanoImage::isValid() const noexcept
+{
+    return (fContext != nullptr && fImageId != 0);
+}
+
 Size<int> NanoImage::getSize() const
 {
     int w=0, h=0;
@@ -119,6 +138,20 @@ void NanoImage::updateImage(const uchar* data)
         nvgUpdateImage(fContext, fImageId, data);
 }
 
+NanoImage NanoImage::operator=(NanoImage img) noexcept
+{
+    if (fContext != nullptr && fImageId != 0)
+        nvgDeleteImage(fContext, fImageId);
+
+    fContext = img.fContext;
+    fImageId = img.fImageId;
+
+    img.fContext = nullptr;
+    img.fImageId = 0;
+
+    return *this;
+}
+
 // -----------------------------------------------------------------------
 // NanoVG